Heaters for use in heating various fluids including liquids and gases in tanks have been known and have been constructed in a variety of different ways. In one form of such heaters, the heater comprises an elongated shell, for instance a cylindrical shell, in which is cast a block of a heat conductive metal, such as aluminum. A plurality of tubes are positioned within the cast metal, being closed at one end and being opened externally of the metal block at the other end. Individual electrical heater elements are positioned in each tube within the block, and provision is made for withdrawing and replacing individual heater elements from the open ends of the heater tubes.
In the present application a heater of the general kind just referred to is sometimes identified as a "block" type heater.
In the arrangement provided by the present invention, the metal of the heater block is cast within a shell, for instance a cylindrical tube, which is closed at one end but which is open at the other end adjacent to the open ends of the tubes for receiving the individual heater elements. An end plate for the heater is provided, being integrally connected, as by welding to the shell of the heater, the end plate having a radially projecting flange adapted for use in the connection of the heater with a tank or other receptacle in which the heater is to be positioned.
According to the present invention, an electrical junction box is provided, being arranged so that the individual heater elements can be removed and replaced, and connected and disconnected to the appropriate power circuit. According to the present invention, this junction box is separated or isolated from the remainder of the heater, including the end plate above referred to; and the end plate is provided with apertures through which the individual heater elements extend, so as to bridge the space between the heater itself and the junction box and project into the junction box.
Packing devices are associated with the heater elements where the elements project through the end plate of the heater itself and also through the adjacent but spaced wall of the junction box, thereby providing for isolation of the junction box from the body of the heater and from the tank or fluid containing structure with which the heater is employed.
The invention, therefore, provides for effective isolation of the junction box from the heater itself while, at the same time, permitting ready withdrawal and replacement of individual heater elements. Indeed, as will appear more fully hereinafter, this ready withdrawal and replacement of heater elements is made possible without hazard of any appreciable contact with the liquid or other fluid being heated, even in the event of accidental leakage of the liquid from the tank into the interior of the heater shell.
The isolation of the junction box from the heater and from the tank or container in which the fluid is contained is of particular importance in connection with equipment used for the heating of a wide variety of liquids, such as oils, viscous materials, such as molasses, or various other liquids or gases having explosive or contaminating characteristics.
In addition to the foregoing, the invention contemplates employment of heat transfer fins on the outside surface of the shell in which the heater block is cast. According to the invention, these fins are extended longitudinally of the shell and may comprise either imperforate or perforated fin elements according to certain particular installations, as will be explained more fully hereinafter. Indeed, for certain purposes the heater of the present invention may even be effectively used without heat transfer fins.